Change a template of an existing wordpress website

Hello there. My website ([login to view URL]) which is for villa rentals and has over 120 posts with 15 photos each went crazy and changed its theme to a normal blog with no photos. Godaddy told me that i am using a very old version of wordpress and that updating it would most likely fix the problem so i need someone who can do this for me but 1st there is a back up to be done. After this is done and i can have go daddy restore my website; i would need someone to help me change my theme to another real estate theme that i found online with wordpress. PLEASE HELP. I need help ASAP.